The present invention relates to a system for controlling the ignition timing of an internal combustion engine such as an automotive engine.
A learning control system for correcting the ignition timing has been proposed. The control system is adapted to advance the ignition timing so as to produce a maximum torque as long as the level of engine knocking does not exceed a tolerable level. The ignition timing stored in a RAM is corrected by a small correcting quantity (quantity of correction) and converges to a desired value little by little. The correcting quantity for the ignition timing at every updating operation is gradually reduced as the ignition timing approaches the desired value.
In order to reduce the correcting quantity, it is necessary to determining that the corrected ignition timing approaches the desired timing. If the decision is not properly made, it takes a long time for the ignition timing to converge to the desired timing.